<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>
      </slot>
    </div>
    <div class="dots">
      <span class="dot" v-for="(item,index) in dots" :class="{active: currentPageIndex === index}"></span>
    </div>
  </div>
</template>

<script type="text/ecmascript-6">
    import BScroll from 'better-scroll'
    import {addClass} from 'common/js/dom'
    export default {
        data(){
            return {
                dots: [],
                currentPageIndex: 0
            }
        },
        props:{
            loop:{
                type: Boolean,
                default: true
            },
            autoPlay:{
                type: Boolean,
                default: true
            },
            interval:{
                type: Number,
                default: 4000
            }
        },
        mounted(){
            setTimeout(() => {
                this._setSliderWidth();
                this._initDots();
                this._initSlider();

                if (this.autoPlay) {
                    this._play()
                }
            }, 20);

            window.addEventListener('resize', ()=>{
                if (!this.slider) {
                    return;
                }
                //浏览器窗口变化的时候，重新设置元素宽度
                this._setSliderWidth(true);
                this.slider.refresh();
            })
        },
        methods:{
            _setSliderWidth(isResize){
                this.children = this.$refs.sliderGroup.children;
                let width=0;
                let sliderWidth = this.$refs.slider.clientWidth;
                for(let i=0;i<this.children.length;i++){
                    let child = this.children[i];
                    addClass(child, 'slider-item');
                    child.style.width = sliderWidth;
                    width += sliderWidth;
                }

                //这里加上两个元素的宽度，因为调用插件的时候会向父级元素中添加两个元素
                //如果屏幕变化，这里为什么不加两个多余的宽度呢？？？
                if (this.loop && !isResize) {
                    width += 2*sliderWidth;
                }
                //设置轮播图的所有元素的宽度为所有图片的宽度之和
                this.$refs.sliderGroup.style.width = width + 'px';
                //图片的宽度太大了，导致floatleft排不到一行去，使用js重新设置一下图片的宽度就好
                let images = this.$refs.sliderGroup.getElementsByTagName('img');
                for (var i = 0; i < images.length; i++) {
                    images[i]['style']['width'] = window.innerWidth + 'px';
                }
            },
            _initDots(){
                //初始化一个五个元素的数组
                this.dots = new Array(this.children.length);
            },
            _initSlider(){
                this.slider = new BScroll(this.$refs.slider, {
                    scrollX:true,
                    scrollY:false,
                    momentum: false,
                    snap: true,
                    snapLoop: this.loop,
                    snapThreshold: 0.3,
                    snapSpeed: 400
                });

                //每次轮播图滑动过去之后记录下来当前轮播图的下标
                this.slider.on('scrollEnd', ()=>{
                    let pageIndex = this.slider.getCurrentPage().pageX;
                    if (this.loop) {
                        pageIndex -= 1;
                    }
                    this.currentPageIndex = pageIndex;

                    //在翻动完了以后重新调用滚动 器
                    if (this.autoPlay) {
                        clearTimeout(this.timer);
                        this._play();
                    }
                })
            },
            //让轮播图自动向前走
            _play(){
                let pageIndex = this.currentPageIndex + 1;
                if (this.loop) {
                    pageIndex += 1;
                }
                this.currentPageIndex = pageIndex;

                this.timer = setTimeout(()=>{
                    this.slider.goToPage(pageIndex, 0, 400);
                },this.interval)
            },
            //在组建销毁的时候，将时间计时器销毁
            destroyed(){
                clearTimeout(this.timer);
            }
        }
    }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"

  .slider
    min-height: 1px
    .slider-group
      position: relative
      overflow: hidden
      white-space: nowrap
      .slider-item
        float: left
        box-sizing: border-box
        overflow: hidden
        text-align: center
        a
          display: block
          width: 100%
          overflow: hidden
          text-decoration: none
        img
          display: block
          width: 100%
    .dots
      position: absolute
      right: 0
      left: 0
      bottom: 12px
      text-align: center
      font-size: 0
      .dot
        display: inline-block
        margin: 0 4px
        width: 8px
        height: 8px
        border-radius: 50%
        background: $color-text-l
        &.active
          width: 20px
          border-radius: 5px
          background: $color-text-ll
</style>
